A known battery pack for an electric vehicle may include an upper case and a lower case jointly defining a battery chamber for containing a battery therein (see, for example, JP2009-146881A, JP2011-194982A, and JP2014-194907A).
The battery pack is often disposed under the floor of the vehicle body, and therefore, is preferably provided with waterproof property, so that the battery in the battery chamber is protected from water in such a case as when the vehicle travels through a puddle or on a flooded road and the battery pack is covered with water splashed by the wheels of the vehicle or the battery pack is partially or entirely submerged in water.
However, conventional battery packs still have room for improving the waterproof property. Particularly, prevention of intrusion of water into the battery chamber when the battery pack is submerged in water should be improved further.